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EN
In this paper, the ability to detect broken rotor bar (BRB) defects in a small renewable energy system (based on a squirrel cage induction generator (SCIG)) by the digital signal processing of captured phase currents, is presented. The new approach proposed in this study is a combination of two techniques. The first technique is a discrete wavelet transform (DWT) by the decomposition of the phase current signal in multilevel frequency bands. This is performed with the analysis of some selected approximations and/or details, which contain both the lower and upper sideband components presenting the characteristic frequency of the BRB fault. The second technique is power spectral density (PSD) analysis. This approach provides the ability to optimize the diagnosis of rotor defects in electrical generators. The results obtained by the proposed DWT-PSD approach are proved and improved by comparing them with the results of the PSD analysis, obtained from the original phase current signal delivered by the 5.7-kW squirrel cage induction generator, based on a small wind energy conversion system.
EN
A thermodynamic analysis of an advanced CAES for Distributed Power Generation (DPG) is presented that utilizes turbomachinery for energy recovery, but also gives continuous power generation to augment on-site power. The advanced CAES uses renewable energy such as wind power and solar PV in the power range of 1500 to 2500 kW plus recuperation of waste heat from the existing on-site prime mover to improve the utility of the energy storage system. The proposed system also utilizes battery storage to maintain high energy density storage, preferably without the need for costly electrical rectifying and inversion systems to improve the stabilization of power generation. This proposed system may be thought of as a “cross-over” system that combines CAES technology with electric battery storage technology, particularly if the stored electric power is used directly as D.C. power at an industrial facility. The direct use of stored energy from a battery as heat input to the proposed “cross-over” system also may be considered in some limited applications. The ideal application of the proposed system is for isolated DPG systems perhaps in remote sites utilizing “power islands” of renewable energy augmented with on-site fossil fuel prime mover, power generation systems. The proposed “cross-over” system enables higher reliability, faster response to transient power loads, and the efficient use of renewable energy, as well as heat recovery from conventional prime mover systems that are on site.
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EN
Local systems, composed of Renewable Energy Sources, generators, loads and storage devices, perform energy transfers between system components. The number of possible configurations of energy transfers grows rapidly with the number of system components, making reliable energy management a difficult task. This paper presents an approach to describe the system operation, according its energy transfers, in form of the automatically generated directed graph. The approach is focused on finding the complete set of all possible system states, that are not prohibited by the operation strategy nor inconsistent. The method is very general and can be applicable to arbitrary system configuration, that can be described at the level of components with only basic attributes and sequences of interactions. Namely, the system components are categorized according to their roles (source/sink/both), fitting in the system (rigid/adaptive) and their persistence (permanent/temporary). The key point of this method is that the final energy transfers diagram is extracted from the initial full graph by filtering out the nodes and transitions not allowed by the defined system operation principle, but leaving all the remaining states. In this way, no consistent system state is overlooked. The generated diagram may be used for studying and visualizing system operation policy, registering the energy flows, discovering doubtful states and transitions or finally for implementation of a reliable energy management controller.
PL
Na terenie kampusu Politechniki Białostockiej powstał hybrydowy system małej energetyki wiatrowej i fotowoltaicznej. Wyjątkowy w skali kraju, jedyny w regionie modelowy system hybrydowego zasilania w energię elektryczną pozwala na analizę zachowania się systemu OZE w warunkach jego normalnej pracy. Celem prowadzonych badań jest obserwacja poziomów napięć i wartości płynących prądów w wybranych punktach pracującego systemu odnawialnej energetyki wiatrowej i fotowoltaicznej sprzężonego z siecią elektroenergetyczną w terenie zurbanizowanym w regionie północno-wschodniej Polski. W artykule przedstawiono wyniki tych obserwacji ze szczególnym zwróceniem uwagi na pojawiające się stany nieustalone mogące skutkować niewłaściwą pracą systemu.
EN
On Bialystok University of Technology campus area small hybrid system power plant was created. It consist of small wind and photovoltaic energy sources. Unique in the country, the only one in the region a real model system of a hybrid power supply allows to analyse the behaviour of the renewable energy system under normal operation conditions. The aim of the research is to monitor the levels of voltages and currents at selected points of system. The results of these observations was presented in paper with particular attention to transients that can cause malfunction of the system. During normal operation renewable wind energy and photovoltaic was coupled to the power grid in urban areas in north-eastern part of Poland.
EN
This paper presents three closed loop control systems for a three-level neutral-point-clamped quasi impedance source inverter. These control systems are designed and simulated to enable validation of their operation for improvement of the capabilities of the three-level neutral-pointclamped quasi impedance source inverter during variable input voltage situations. PID controller-based control systems could be used in photovoltaic applications in which the output voltage of the solar array depends on the irradiance and the temperature produces variable input voltage.
PL
W artykule przedstawiono trzy algorytmy sterowania w pętli zamkniętej, bazujące na regulatorach PID, dla trójpoziomowego przekształtnika z diodami poziomującymi zasilanego ze źródła quasi-Z. Przeprowadzono badania symulacyjne omawianych algorytmów, w celu potwierdzenia ich pozytywnego wpływu na pracę przekształtnika w warunkach zmienności napięcia wejściowego. Proponowane strategie mają potencjalne zastosowanie w fotowoltaice, gdzie występują zmiany napięcia wyjściowego w zależności od temperatury i nasłonecznienia.
EN
The majority of renewable energy sources deliver relatively low output voltage. In renewable energy systems high-efficiency high voltage gain step-up DC-DC converters are required as the interface between low voltage sources and the load. Therefore overall performance of the renewable energy system is strongly affected by the efficiency of step-up DC-DC converter itself. This paper presents high-efficiency interleaved step-up DC-DC converter with coupled inductors. Interleaved approach minimizes the current stress of the switches as well as the a sizes of the inductors but also allows reducing input current ripples. The other advantage of interleaving structure is the flexibility of number of phases extension. The number of working phases can be determined depending on the power requirements of the load. High efficiency is achieved by recycling the energy from leakage inductance present in practical coupled inductors. In order to re-use leakage energy voltage clamp circuit is applied. It allows to minimize voltage stress across the switches further improving the efficiency of interleaved DC-DC converter. The simulation carried out will present parametric and performance characteristics of the converter. Most efficient configuration and the number of phases will be discussed in this paper.
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